Iron titanium manganase alloy hydrogen storage

ABSTRACT

A three component alloy capable of reversible sorption of hydrogen having the chemical formula TiFe1 x Mnx where x is in the range of about 0.02 to 0.5 and the method of storing hydrogen using said alloy.

United States Patent Reilly et al.

Dec. 2, 1975 IRON TITANIUM MANGANASE ALLOY HYDROGEN STORAGE Inventors:James J. Reilly, Bellport; Richard H.

Wiswall, ,Ir., Brookhaven, both of N.Y.

Assignee: The United States of America as represented by the UnitedStates Energy Research and Development Administration, Washington, DC.

Filed: Feb. 4, 1975 Appl. No.: 547,073

US. Cl. 62/48; 75/134 F; 75/l75.5;

252/471; 423/248 Int. Cl. F17C 11/00 Field of Search 62/48; 75/1755, 134F;

Primary Examirter-Will1am F. ODea Assistant ExaminerRonald C. CaposselaAttorney, Agent, or Firm-Dean E. Carlson; Leonard Belkin [57] ABSTRACT Athree component alloy capable of reversible sorption of hydrogen havingthe chemical formula TiFe, Mn, where x is in the range of about 0.02 to0.5 and the method of storing hydrogen using said alloy.

4 Claims, 2 Drawing Figures lllllll lllllll N I e 3 Lu 10: I D (D m uJQ: CL

z Q 6 1.0: o I m 2 Q OJ 1 l l l ATOM RATIO, H/M

IRON TITANIUM MANGANASE ALLOY HYDROGEN STORAGE BACKGROUND OF THEINVENTION The invention described herein was made in the course of, orunder a contract with the US Atomic Energy Commission.

Hydrogen is a potential fuel for various types of power sources, such asfuel cells, internal combustion 1O engines, gas turbines, etc. It hastwo great advantages over fossil fuels, it is essentially nonpollutingand it can be produced using several all but inexhaustible energysources, i.e., solar, nuclear and geothermal. However, a major problemis the difficulty encountered in its storage and bulk transport.Conventional storage methods, i.e., compression and liquefaction, do notappear to be practical in this context.

A possible solution to the problem lies in the use of a metal hydride asa hydrogen storage medium. Several hydrides are of interest but thematerial most near to practical application is iron titanium hydride,which can be synthesized through the direct union of hydrogen with theintermetallic compound, FeTi.

Our US. Pat. Nos. 3,508,414 and 3,516,263 disclose methods and apparatusfor utilizing iron-titanium alloys to store hydrogen by the formation ofhydrides.

One difficulty which has been discovered in the use of iron-titaniumalloys for hydrogen storage is the effect of the presence of oxygen inthe alloys in small amounts. For example, it has been discovered thatthe presence of oxygen in the amount of 7000 ppm in commerciallyavailable iron-titanium reduced substantially the maximum hydrogen thatcould be stored and the equilibrium dissociation pressure was increased.This had the effect of increasing the costs involved in storing hydrogenby the use of these alloys.

SUMMARY OF THE INVENTION It has been discovered that the addition ofmanga nese to the intermetallic alloy FeTi in certain specific amountsnot only increases the amount of H which can be stored and at a lowerpressure but also has the effect of compensating to a significant extentfor the presence of oxygen, permitting significant increases in theamounts of hydrogen which can be stored under more convenient andeconomical pressures.

In accordance with a preferred embodiment of this invention there isprovided a three component alloy capable of reversible sorption ofhydrogen having the chemical formula TiFe Mn where x is in the range ofabout 0.02 to 0.5.

There is also provided, in accordance with another preferred embodimentof this invention, a method of storing hydrogen comprising contactinggaseous hydrogen with a solid alloy of TiFe Mn, where x is in the rangeof about 0.02 to 0.5.

It is thus a principal object of this invention to provide an improvedalloy for the chemical storage of hydrogen.

Another purpose is to provide an improved method for the storage ofhydrogen.

Other objects and advantages of this invention will hereinafter becomeobvious from the following description of preferred embodiments of thisinvention.

BRIEF DESCRIPTION OF THE DRAWING FIGS. 1 and 2 show curves illustratingthe H storage characteristics of alloys incorporating the principles ofthis invention and comparing them with similar alloys not incorporatingthis invention.

DESCRIPTION OF THE BACKGROUND EMBODIMENTS An alloy in accordance withthis invention may be prepared by melting granules or small ingots ofFe, Ti, and Mn in an are or induction furnace within an inert atmospherefollowed by cooling.

The cooled alloy, in order to be utilized for the storage of hydrogen iscomminuted or granulated and then activated by outgassing at hightemperature (300 C) and exposing to H for a short time followed byoutgassing again and cooling under hydrogen with about 1 atmospherepressure.

In order to form the hydride the activated alloy is exposed to H at apressure usually 10 atmospheres above dissociation pressure at thattemperature, due to hysteresis type effects. The hydriding pressureshould for best results be at least twice the dissociation pressurebecause of the already mentioned hysteresis effect.

EXAMPLES An alloy was prepared with the composition (A) of FeTi and thedissociation pressure-composition isotherms for this alloy are shown inFIG. 1. The H dissociation pressure of this alloy can be seen from thecurve at 40 C to be at least 7.2 atmospheres and reaches 25 atmospheresat the maximum H concentration. A similar alloy (B) was prepared inwhich some of the iron was displaced by Mn and had the formula TiFe MnThe dissociation pressures for this alloy at the same temperature, asshown in FIG. 1, range from 0.42 to 9 atmospheres for the same amount ofstored H as in alloy (A). In the drawing, the atom ratio, H/M is definedas the ratio of atoms of hydrogen to total atoms of metal.

It was found that for other temperature conditions the presence of Mndisplacing some of the iron additionally made it possible to increasethe amount of H which could be stored as well as reducing thedissociation pressure. Curves C in FIG. 2 shows isotherms for a FeTialloy at 55 and C'while curve D shows the isotherm at 61 C for thecomposition TiFe Mn Not only does alloy D have a lower dissociationpressure but in addition H storage capacity was increased by about 10percent by weight. This is shown by the upper limits of the curve.

What is claimed is:

1. A three component alloy capable of reversible sorption of hydrogenhaving the chemical formula TiFe Mn, where x is in the range of about0.02 to 0.5.

2. The method of storing hydrogen comprising contacting a solid alloy ofTiFe Mn, where x is in the range of about 0.02 to 0.5 with gaseous H ata pressure above the dissociation pressure of the hydride.

3. The method of claim 2 in which the pressure of H during contacting isat least twice the dissociation pressure of the hydride for thetemperature during contactmg.

4. The method of claim 3 in which the pressure of H during contacting isabout ten times the dissociation pressure of the hydride for thetemperature during contacting.

1. A three component alloy capable of reversible sorption of hydrogenhaving the chemical formula TiFe1 xMnx where x is in the range of about0.02 to 0.5.
 2. THE METHOD OF STORING HYDROGEN COMPRISING CONTACTING ASOLID ALLOY OF TIFE1-XMNX WHERE X IS IN THE RANGE OF ABOUT 0.02 TO 0.5WITH GASEOUS H2 AT A PRESSURE ABOVE THE DISSOCIATION PRESSURE OF THEHYDRIDE.
 3. The method of claim 2 in which the pressure of H2 duringcontacting is at least twice the dissociation pressure of the hydridefor the temperature during contacting.
 4. The method of claim 3 in whichthe pressure of H2 during contacting is about ten times the dissociationpressure of the hydride for the temperature during contacting.